"Own your power," Harris said, following a panel discussion at an event hosted by the women's leadership platform MAKERS during Advertising Week. "In your 20s, you start to doubt what it is you can do. You doubt why you're in the room. But you're in the room."

The executive said that if you have been given an opportunity, seize it.

"If you got invited to the room, and certainly if you got invited to the table, you are all that," she said. "And you should own that."

Harris was appointed by President Barack Obama in 2013 to chair the National Women's Business Council and has written career guides "Expect to Win" and "Strategize to Win."